虚拟同步发电机接入弱电网的序阻抗建模与稳定性分析
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摘要
虚拟同步发电机(virtual synchronous generator,VSG)按照控制方法的不同可分为电压控制型和电流控制型VSG。首先,采用谐波线性化方法建立电压控制型VSG和电流控制型VSG的小信号序阻抗模型,对比分析这两种不同类型VSG的序阻抗特性。电压控制型VSG的序阻抗基本呈感性,与电网的阻抗特性基本一致;而电流控制型VSG的序阻抗在中频段显负阻性,且阻抗幅值非常小。基于所建序阻抗模型和Nyquist稳定判据分析电网强弱、VSG并网台数和锁相环带宽对两种不同类型VSG并网系统稳定性的影响。稳定性分析结果表明:电流控制型VSG接入电网容易发生谐波振荡问题,而电压控制型VSG并网系统在弱电网或者高渗透率新能源发电下依旧可以稳定运行且无锁相环的约束。因此,从系统稳定性的角度来说,电压控制型VSG比电流控制型VSG更适合应用于新能源并网发电中。实验验证了该文分析的正确性。
The virtual synchronous generator(VSG) can be divided into voltage control type and current control type of VSG according to different control methods. Firstly, the small-signal sequence impedance model of the two types of VSG was built by using harmonic linearization method. Then,the sequence impedance characteristics of these two different types of VSG were compared and analyzed. The sequence impedance of voltage controlled type of VSG is basically inductive and consistent with the impedance characteristics of the grid. However, the sequence impedance of current controlled type of VSG is mainly negative resistive in the middle-frequency area and the impedance amplitude is quite low. Then, based on the built sequence impedance model and the impedance stability criterion, the influence of the grid stiffness, the parallel number of VSGs and phase locked loop(PLL) bandwidth on the stability of the two different VSG grid-connected system was analyzed. The stability analysis results show that the current controlled type of VSG loses stability easily while the voltage controlled type of VSG still works well and with no PLL restriction under the weak grid condition or with large number of VSGs connected to the grid.Therefore, the voltage controlled type of VSG is more suitable to achieve renewable energy grid-connected generation than the current controlled type of VSG from the point of view of system stability. Finally, experiment results validate the analysis.
The virtual synchronous generator(VSG) can be divided into voltage control type and current control type of VSG according to different control methods. Firstly, the small-signal sequence impedance model of the two types of VSG was built by using harmonic linearization method. Then,the sequence impedance characteristics of these two different types of VSG were compared and analyzed. The sequence impedance of voltage controlled type of VSG is basically inductive and consistent with the impedance characteristics of the grid. However, the sequence impedance of current controlled type of VSG is mainly negative resistive in the middle-frequency area and the impedance amplitude is quite low. Then, based on the built sequence impedance model and the impedance stability criterion, the influence of the grid stiffness, the parallel number of VSGs and phase locked loop(PLL) bandwidth on the stability of the two different VSG grid-connected system was analyzed. The stability analysis results show that the current controlled type of VSG loses stability easily while the voltage controlled type of VSG still works well and with no PLL restriction under the weak grid condition or with large number of VSGs connected to the grid.Therefore, the voltage controlled type of VSG is more suitable to achieve renewable energy grid-connected generation than the current controlled type of VSG from the point of view of system stability. Finally, experiment results validate the analysis.
引文
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[22]Sun Jian,Liu Hanchao.Sequence impedance modeling of modular multilevel converters[J].IEEE Journal of Emerging and Selected Topics in Power Electronics,2017,5(4):1427-1443.
[23]Liu Hanchao,Sun Jian.Voltage stability and control of offshore wind farms with AC collection and HVDCtransmission[J].IEEE Journal of Emerging and Selected Topics in Power Electronics,2014,2(4):1181-1189.
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[25]伍文华,陈燕东,罗安,等.海岛VSC-HVDC输电系统直流阻抗建模、振荡分析与抑制方法[J].中国电机工程学报,2018,38(15):4359-4368,4636.Wu Wenhua,Chen Yandong,Luo An,et al.DC impedance modeling,oscillation analysis and suppression method for VSC-HVDC system in the field of islands power supply[J].Proceedings of the CSEE,2018,38(15):4359-4368,4636(in Chinese).
[26]陈燕东,罗安,龙际根,等.阻性逆变器并联环流分析及鲁棒下垂多环控制[J].中国电机工程学报,2013,33(18):18-29.Chen Yandong,Luo An,Long Jigen,et al.Circulating current analysis and robust droop multiple loop control method for parallel inverters using resistive output impedance[J].Proceedings of the CSEE,2013,33(18):18-29(in Chinese).
[2]Alawasa K M,Mohamed Y A I.A simple approach to damp SSR in series-compensated systems via reshaping the output admittance of a nearby VSC-based system[J].IEEE Transactions on Industrial Electronics,2015,62(5):2673-2682.
[3]吕志鹏,盛万兴,刘海涛,等.虚拟同步机技术在电力系统中的应用与挑战[J].中国电机工程学报,2017,37(2):349-360.LüZhipeng,Sheng Wanxing,Liu Haitao,et al.Application and challenge of virtual synchronous machine technology in power system[J].Proceedings of the CSEE,2017,37(2):349-360(in Chinese).
[4]D'Arco S,Suul J A.Virtual synchronous machinesclassification of implementations and analysis of equivalence to droop controllers for microgrids[C]//Proceedings of 2013 IEEE Grenoble Conference.Grenoble,France:IEEE,2013:1-7.
[5]Wang Dongxu,Wu Hongbin.Application of virtual synchronous generator technology in microgrid[C]//Proceedings of the IEEE 8th International Power Electronics and Motion Control Conference.Hefei,China:IEEE,2016:3142-3148.
[6]Zhong Qingchang,Weiss G.Synchronverters:inverters that mimic synchronous generators[J].IEEE Transactions on Industrial Electronics,2011,58(4):1259-1267.
[7]吕志鹏,盛万兴,钟庆昌,等.虚拟同步发电机及其在微电网中的应用[J].中国电机工程学报,2014,34(16):2591-2603.LüZhipeng,Sheng Wanxing,Zhong Qingchang,et al.Virtual synchronous generator and its applications in micro-grid[J].Proceedings of the CSEE,2014,34(16):2591-2603(in Chinese).
[8]Shuai Zhikang,Huang Wen,Shen Chao,et al.Characteristics and restraining method of fast transient inrush fault currents in synchronverters[J].IEEETransactions on Industrial Electronics,2017,64(9):7487-7497.
[9]伍文华,陈燕东,罗安,等.一种直流微网双向并网变换器虚拟惯性控制策略[J].中国电机工程学报,2017,37(2):360-372.Wu Wenhua,Chen Yandong,Luo An,et al.A virtual inertia control strategy for bidirectional grid-connected converters in DC micro-grids[J].Proceedings of the CSEE,2017,37(2):360-372(in Chinese).
[10]吕志鹏,梁英,曾正,等.应用虚拟同步电机技术的电动汽车快充控制方法[J].中国电机工程学报,2014,34(25):4287-4294.LüZhipeng,Liang Ying,Zeng Zheng,et al.Virtual synchronous motor based control scheme of fast charger for electric vehicle application[J].Proceedings of the CSEE,2014,34(25):4287-4294(in Chinese).
[11]Wang Shuo,Hu Jiabing,Yuan Xiaoming,et al.On inertial dynamics of virtual-synchronous-controlled DFIG-based wind turbines[J].IEEE Transactions on Energy Conversion,2015,30(4):1691-1702.
[12]Aouini R,Marinescu B,Kilani K B,et al.Synchronverter-based emulation and control of HVDCtransmission[J].IEEE Transactions on Power Systems,2016,31(1):278-286.
[13]Wu Heng,Ruan Xinbo,Yang Dongsheng,et al.Small-signal modeling and parameters design for virtual synchronous generators[J].IEEE Transactions on Industrial Electronics,2016,63(7):4292-4303.
[14]Du Yan,Guerrero J M,Chang Liuchen,et al.Modeling,analysis,and design of a frequency-droop-based virtual synchronous generator for microgrid applications[C]//Proceedings of 2013 IEEE ECCE Asia Downunder.Melbourne,VIC:IEEE,2013:643-649.
[15]颜湘武,刘正男,张波,等.具有同步发电机特性的并联逆变器小信号稳定性分析[J].电网技术,2016,40(3):910-917.Yan Xiangwu,Liu Zhengnan,Zhang Bo,et al.Small-signal stability analysis of parallel inverters with synchronous generator characteristics[J].Power System Technology,2016,40(3):910-917(in Chinese).
[16]Hu Changbin,Chen Kaiyu,Luo Shanna,et al.Small signal modeling and stability analysis of virtual synchronous generators[C]//Proceedings of the 20th International Conference on Electrical Machines and Systems.Sydney,Australia:IEEE,2017.
[17]Zhong Qingchang,Nguyen P L,Ma Zhenyu,et al.Self-synchronized synchronverters:inverters without a dedicated synchronization unit[J].IEEE Transactions on Power Electronics,2014,29(2):617-630.
[18]Wen Bo,Boroyevich D,Burgos R,et al.Analysis of D-Qsmall-signal impedance of grid-tied inverters[J].IEEETransactions on Power Electronics,2016,31(1):675-687.
[19]Cespedes M,Sun Jian.Impedance modeling and analysis of grid-connected voltage-source converters[J].IEEETransactions on Power Electronics,2014,29(3):1254-1261.
[20]Sun Jian.Impedance-based stability criterion for grid-connected inverters[J].IEEE Transactions on Power Electronics,2011,26(11):3075-3078.
[21]王赟程,陈新,陈杰,等.基于谐波线性化的三相LCL型并网逆变器正负序阻抗建模分析[J].中国电机工程学报,2016,36(21):5890-5898.Wang Yuncheng,Chen Xin,Chen Jie,et al.Analysis of positive-sequence and negative-sequence impedance modeling of three-phase LCL-type grid-connected inverters based on harmonic linearization[J].Proceedings of the CSEE,2016,36(21):5890-5898(in Chinese).
[22]Sun Jian,Liu Hanchao.Sequence impedance modeling of modular multilevel converters[J].IEEE Journal of Emerging and Selected Topics in Power Electronics,2017,5(4):1427-1443.
[23]Liu Hanchao,Sun Jian.Voltage stability and control of offshore wind farms with AC collection and HVDCtransmission[J].IEEE Journal of Emerging and Selected Topics in Power Electronics,2014,2(4):1181-1189.
[24]Anwar T,Vieto I,Sun Jian.Automated sequence impedance modeling of three-phase converters based on computer algebra[C]//Proceedings of the 43rd Annual Conference of the IEEE Industrial Electronics Society.Beijing,China:IEEE,2017:904-909.
[25]伍文华,陈燕东,罗安,等.海岛VSC-HVDC输电系统直流阻抗建模、振荡分析与抑制方法[J].中国电机工程学报,2018,38(15):4359-4368,4636.Wu Wenhua,Chen Yandong,Luo An,et al.DC impedance modeling,oscillation analysis and suppression method for VSC-HVDC system in the field of islands power supply[J].Proceedings of the CSEE,2018,38(15):4359-4368,4636(in Chinese).
[26]陈燕东,罗安,龙际根,等.阻性逆变器并联环流分析及鲁棒下垂多环控制[J].中国电机工程学报,2013,33(18):18-29.Chen Yandong,Luo An,Long Jigen,et al.Circulating current analysis and robust droop multiple loop control method for parallel inverters using resistive output impedance[J].Proceedings of the CSEE,2013,33(18):18-29(in Chinese).